A gas turbine engine typically comprises a multi-stage compressor that compresses air, which has been drawn into the engine, to a higher pressure and temperature. A majority of this air passes to the combustion system, which mixes the compressed and heated air with fuel and contains the resulting reaction that generates the hot combustion gases. These gases then pass through a multi-stage turbine, which, in turn drives the compressor, and possibly a shaft of an electrical generator. Exhaust from the turbine can also be channeled to provide thrust for propulsion of a vehicle.
Typical compressors and turbines comprise a plurality of alternating rows of rotating and stationary airfoils. An example of a vane segment, or stator section, comprising a plurality of airfoils positioned between an inner platform and outer platform is shown in FIG. 1. In this embodiment of the prior art, the vane segment spans approximately 180 degrees where two vane segments together encompass an engine shaft (not shown) which runs along the engine centerline. A vane segment 10 of the prior art, is shown in FIG. 1, and comprises an inner platform 12, an outer platform 14, and vanes 16 extending between inner platform 12 and outer platform 14. The vane segment 10 encompasses approximately 180 degree span and is in accordance with typical vane styles of the prior art.
The stationary airfoils, or vanes, direct the flow of air in a compressor or hot combustion gases in a turbine onto a subsequent row of rotating airfoils, or blades, at the proper orientation in order to maximize the output of the compressor or turbine. To minimize manufacturing costs as well as to improve response to thermal gradients and thermal deflections, more recent engine designs utilize a plurality of vane assemblies in the compressor or turbine. These vane assemblies include at least one airfoil bounded on either end by a section of an outer platform and an inner platform, with the inner platform located closer to the engine centerline. Each of the vane assemblies typically span a few degrees and have a shorter arc length than the prior art half-ring segments. Depending on how the vane assemblies are mounted in the engine, significant movement can occur between adjacent vane assemblies causing undesirable contact and wear. When vane assemblies are mounted at or near their outer platform, thereby causing them to essentially hang free at the inner platform, relatively large movement can occur at the inner platform due to the distance of the inner platform from the mounting location, vibrations, and differences in thermal gradients between the adjacent vane assemblies. When such motion occurs between adjacent vane assemblies, significant wear can occur along the mating surfaces due to the mating surfaces essentially damping the vibrations. Significant wear is also found at the hooks that hold the vane assemblies in place due to the amount of movement at the inner platform and the surface-to-surface contact at the mounting location. This excessive wear can lead to premature repair or require replacement of the vane assemblies.
What is needed is a vane assembly configuration that reduces the amount of wear that occurs along mating faces of adjacent vane assemblies and at the mounting location so as to increase the life of the vane assemblies.